This invention relates to a subsurface signal transmitting apparatus of the type for sensing certain conditions in a bore hole and then transferring them to a surface located receiver.
In the oil industry, it is necessary to obtain and analyze down-hole conditions, such as pressures and temperatures at various elevations. This has been done most commonly in the past by lowering electrically or mechanically operated gauge devices into the well, these gauges being either suspended on a wire line or fastened to available oil well tubular sections. By utilizing conductor wire lines, the information can be transmitted to the surface on a xe2x80x9creal-timexe2x80x9d basis. When non-conductor lines are employed, the gauge must be withdrawn to the surface so that the data can be either down-loaded to a plotter or read directly from an internally scribed chart, thus providing the operator with the desired information. In this process, whether the wire line is used as a suspension member or is strapped to the outside of tubular sections forming a string in the bore hole, damaging of the wire line is not uncommon. The damage or destruction of the wire line can occur when the string of tubular sections sticks within the bore hole, or when the wire line and/or tubing string is being run in or out of the hole. Not only is there the cost of the lost equipment, but such damage adds significantly to the cost of the operation because of the time involved in repairing the equipment and in fishing the equipment from the hole. The process of having to fish also includes the risk of endangering the well itself.
Other techniques have been developed for transmitting signals which are produced by apparatus located down-hole to the surface, including devices which develop and transmit signals electromagneticly to the surface. Such signals having been received by a receiving apparatus provide instantaneously information on the conditions sensed down-hole. This telemetry technique involves locating down-hole relatively complex equipment and providing a source of power. Structures have been developed for containing such equipment and power source. These structures enable the use of a portion of the tubing string to function as an antenna in the transmission of the signals to the surface. The process of using the tubing string, such as the upper portion of the string, as the antenna involves the provision of a connection which electrically isolates the upper portion from a lower portion of the tubing string so that the output voltage of the down-hole electromagnetic transmitters can be connected across terminals which are electrically isolated from each other.
The approach of using a telemetry technique for transmitting the information to the surface provides instantaneous readings at a set location of the down-hole sensing equipment and also avoids the use of a wire line. While having significant advantages over other techniques, problems due to the conditions which exist in the bore hole have in many respects hindered successful development in this process. For example, although there exists insulation couplers for use in an arrangement where the upper portion of the tubing is used as an antenna, such couplers have not always functioned satisfactory when the lower portion of the tubular string becomes jammed in the bore hole. This is not uncommon particularly where the lower part of the bore hole deviates from the vertical. Present insulation couplers have not been known to withstand the application of a high torque used in attempting to force the string when jammed, and a severing of the tubing string at the insulation connector results in the lower portion of the tubular string, which houses the expensive telemetry sensing and telemetry equipment, becoming completely disconnected at its down-hole position. Not only is the cost of the equipment involved, but there is the expense involved in reopening the hole and potential damage to the well.
Moreover, due to the nature of the sensing, power source and transmitting equipment utilized in the telemetry process and the extreme conditions to which the down-hole end of the tubing string is subjected, known methods of mounting such equipment has not always proved satisfactory. While the equipment must be protected, the manner in which it is carried and its connection to the insulation connector must be such that it is readily available for exchanging and servicing.
Yet another characteristic of some known structures incorporating an insulation coupler is that they are not capable of coping with particular conditions which can develop either above or below the test equipment when located down-hole. The down-hole test equipment is frequently used in conjunction with annular sealing packers, and in the known structures the insulation connector and/or the test equipment and mounting elements, together with the sealing packers in effect form a complete seal or blockage in the bore hole. Accordingly, in the event a pressure build-up develops either above or below the sealing packers, the tubing string can be sucked into or blown out of the bore hole. This can happen with sufficient force to cause severe injury to personnel and damage to equipment.
It is an object of the present invention to provide an apparatus for subsurface telemetry signal transmission which overcomes the above described disadvantage of known devices presently available in this technology.
According to one aspect of the present invention, which resides in a connector assembly for connection in a tubing string in a bore hole, the connector assembly electrically insulates an upper section of the string above the connector assembly from a lower section below the connector assembly. The assembly includes an outer housing member and an inner mandrel member.
In one form of the connector assembly the housing member has connection means adjacent one end of the connector assembly for attachment of the one end to one of the above mentioned sections of the string, and the housing member has an internal surface portion defining an opening tapering outwardly in cross-sectional area toward that end of the connector assembly. The mandrel member has connection means adjacent the other end of said connector assembly for attachment of that end of the connector assembly to the other of the above mentioned sections of the tubular sting, and the mandrel member has an exterior surface portion tapering outwardly in cross-sectional area away from that end of said connector assembly. The exterior surface portion of the mandrel member is disposed within the interior surface portion of the housing member and provides a clearance between said surface portions. The connector assembly further includes an electrically non-conducting binder material disposed within the clearance.
It is apparent that in the use of this form an insulation connector of the present invention, the outer housing, which may be connected to the upper portion of the tubular string, for example, can function as an antenna for transmitting signals received from equipment mounted in a carrier section connected to the mandrel member. In the case of a tension force being applied to the connector assembly, shear forces are developed in the binding located in the clearance, but the binding is also in compression between the two tapered surface portions of the housing and mandrel members. Moreover, because of the direction of taper relative to the connection means at the opposite ends of the connection assembly, the mandrel member cannot be pulled through the housing member due to an excessive tensional pull on the tubular string. Even on failure of the binding in the clearance, the tensional pull results only in the surface portions moving towards an engaging position.
In another form of the present invention, the housing member has a first connector means adjacent one end of the connector assembly for attachment to an adjacent tubular section of the string above the connector assembly and the inner mandrel member has a second connection means for attachment to an upper end of an instrument carrier device, the mandrel member being of tubular form defining a central passageway extending from said one end to said other end of said connector assembly. Means is provided for electrically insulating the housing member from the mandrel member. The carrier device includes an elongated tubular member having channels in the exterior surface thereof for accommodating instrument sensing units. The tubular member also has an internal passageway disposed therein and placing a lower end thereof in communicating with said passageway in said mandrel member at the upper end thereof. The tubular member has a third connection means at a lower end thereof for attachment of the carrier device to an adjacent section of the tubing string below said carrier device. An electrically insulating by-pass tube extends through the passageways of said mandrel and said carrier device and has fourth and fifth connector means at upper and lower ends thereof, respectively, for connection of the by-pass tube to the tubular sections above and below the apparatus, thus permitting fluid passage through said apparatus.
In this structure, the by-ass tube extending through the passageways in both the connector assembly and the carrier device provides for fluid communication past the subsurface transmitting apparatus so that pressure build-up either above or below the apparatus is prevented, and accordingly the destructive results which can result from such build-up is avoided.
According to another aspect of the invention, there is provided a carrier device for use in a subsurface signal transmitting apparatus, the carrier device being in the form of an elongated body member having a generally cylindrical outer surface. A first connection means is located at one end of said body member for attachment of the body member to an insulation connector assembly having an outer housing member electrically insulated from the body member. The body member has defined in the outer surface thereof a plurality of longitudinal channels commencing adjacent the one end and extending towards an opposite end of said body member. Means are provided for detachably securing instrument sensing units individually within the channels, and a passage extends from said channels to the one end of the body and accommodates a signal transmitting cable extending from the units for electrical attachment to the outer housing of said insulation connector assembly.
The carrier device is capable of being attached to an end of an insulated connector assembly, such as that described above, and more particularly to the connection means provided by the mandrel, so that sensing units which include a transmitting component, can be readily inserted and retrieved from the channels in which they are protected from damage by engagement of the carrier with the sides of the bore hole. The cable which carries the signals to be transmitted can then be located in the provided passage and connected to the antenna providing member of the connection assembly.